Today in Astronomy 142 - Astro Pas Rochester

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Energy sources for the SunChemical energy (burning) doesn’t work.“The Sun is nothing but a burning ember:” Anaxagoras ofClazomenae, ca. 450 BC.Suppose (optimistically) that the Sun were made of anthracitecoal, with enough oxygen to burn it completely to CO 2 :5.5x10 32 gm coal, 1.45x10 33 gm O. Burning 1 gm of anthracitecoal to CO 2 liberates 4.3x10 11 erg. Thus the Sun’s initialenergy reserve would beΔE =4.3x10 11 x 5.5x10 32 erg = 2.4 x 10 44 ergwhich at the Sun’s present luminosity would lastAstronomy 142 28
Energy sources for the Sun (continued)Collapse and liberation of gravitational potential energyalso doesn’t work (Kelvin and Helmholtz, late 19th century):However, mass energy would work, even if only 0.1% of itcould be converted to radiation:Astronomy 142 29
Page 1 and 2: Today in Astronomy 142More on the S
Page 3 and 4: In detail:absorption linesare also
Page 5 and 6: Radiation transportkeeping track of
Page 7 and 8: Mean free pathκopacity units g -1
Page 9 and 10: Opacity depends onwavelength becaus
Page 12 and 13: Solar “granulation:” the tops o
Page 14 and 15: Using Adaptive Optics to look at de
Page 16 and 17: Further out: the corona and chromos
Page 18 and 19: Sunspots: solar magnetismFigure: Ch
Page 20 and 21: Sunspot progress, activity during s
Page 22 and 23: 11-year sunspot cycle, for the last
Page 24 and 25: Sunspot formation and cycle: intera
Page 26 and 27: Cooling timescaleAstronomy 142 26
Page 30 and 31: Energy sources for the Sun (continu

Today in Astronomy 142 - Astro Pas Rochester

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